Method for processing photographic products comprising a fine-grain top layer

ABSTRACT

PCT No. PCT/EP93/00535 Sec. 371 Date Aug. 31, 1994 Sec. 102(e) Date Aug. 31, 1994 PCT Filed Mar. 9, 1993 PCT Pub. No. WO93/19397 PCT Pub. Date Sep. 30, 1993The present invention relates to a color photographic processing method, and a product for color photography comprising, in addition to the conventional layers of light-sensitive silver halides, a non light-sensitive top layer. The method and photographic product enable sensitivity to be controlled during photographic processing. The invention also makes it possible to prevent deterioration of the processing baths.

The present invention relates to a color photographic processing method,and a product for color photography comprising, in addition to theconventional light-sensitive silver halide layers, a top layer which isinsensitive to light.

U.S. Pat. No. 4,596,764 describes a photographic processing method whichconsists of bringing into contact, during the photographic processing, aproduct comprising light-sensitive silver halide emulsion layers with ahigh iodide content and an emulsion layer which is not sensitive tolight with an amino compound (I) of the formula: ##STR1## wherein Mrepresents a hydrogen atom, an alkali metal, an alkaline earth metal, aquaternary ammonium group, a quaternary phosphonium group, an amidinogroup or a group of the formula ##STR2## wherein R¹ and R² eachrepresent separately a hydrogen atom or an aliphatic group, and mrepresents an integer between 2 and 4; or with a strong acid salt.

The protective layer described in this patent comprises a fine-grainemulsion with an iodide content of less than 3% molar, the quantity laiddown to form this top layer being between 50 and 140% molar of the totalquantity of silver iodide in the light-sensitive layers. It is clear inthe art that when a photographic product contains a large quantity ofsilver iodide, the fixing has a reduced efficiency related to the lowsolubility of the silver iodide. The method described in the patentcited above proposes to avoid the problem encountered during the fixingstage by processing the color photographic product described above inthe presence of a compound (I).

The examples in U.S. Pat. No. 4,596,764 show that, in the presence of acompound (I), the best sensitometric results are obtained when theprotective layer consists of a pure bromide emulsion or a pure chlorideemulsion with very fine halide grains, of the order of 0.07 μm, withhowever a slight increase in fogging. In all the examples, thephotographic products contain at least 5% molar of silver iodide in eachlight-sensitive layer. After exposure, these products are brought intocontact with a compound of formula (I) by means of a separate bath usedbefore the bleaching and fixing baths.

U.S. Pat. No. 4,640,890 describes a color photographic productcomprising a base, at least one red-sensitive layer, one green-sensitivelayer and one blue-sensitive layer, with, in at least one of thesesensitive layers, a monodisperse emulsion. The photographic productcomprises moreover an additional layer consisting of a nonlight-sensitive silver halide emulsion with a chloride content greaterthan 75% molar. This additional layer makes it possible to decrease thevariations in the sensitometric characteristics during the processing.In fact, it has been found that the sensitometric characteristics varygreatly according to the agitation of the developer.

The examples in U.S. Pat. No. 4,640,890 show the differences insensitivity and contrast of the product of the invention processed in anagitated developer and in a non-agitated developer. It can be noted thatthe higher the chloride content, the smaller are the variations in thesensitometric characteristics. These results are even more improved whenthe additional layer contains a rhodium salt.

The present invention makes it possible to remedy the problem ofvariations in sensitivity due to contamination of the baths duringautomatic processing of the photographic products. In fact, in someautomatic processing machines, the photographic products pass from onebath to another by means of a conveyor belt made from plastic materialsuch as polypropylene or nylon. These plastic materials at the same timeconvey small quantities of chemical compounds contained in thephotographic baths. These compounds conveyed on the belt contaminate thedifferent photographic baths during the remainder of the processing. Forexample, it has been observed that certain bleaching acceleratorcompounds, initially present in the bleaching or bleach-fixing baths,are partly conveyed on the conveyor belt and are then reintroduced intothe developer. The presence of this type of compound in the developerhas a bad effect on the sensitometric properties of the photographicproducts thus processed.

FIGS. 1, 2, 3, 4 and 5 show the variations in the sensitometriccharacteristics of the photographic products described in the followingexamples versus the quantity of contaminant in the developer.

The object of the present invention is a method for controlling, duringphotographic processing, the sensitivity of a color photographic productby preventing an excessively rapid deterioration of the first developer.The method consists of processing an exposed color product comprising abase, at least one light-sensitive silver halide emulsion layer and atop layer of non light-sensitive silver halide emulsion by means of aprocess comprising at least one developing stage and one bleaching orbleach-fixing stage, the method being characterised in that (A) the toplayer of the photographic product consists of an emulsion comprisingsilver halide grains having a size of less than 0.5 μm and a bromidecontent of between 30 and 70% molar, and (B) the processing is carriedout in the presence of a compound (1) which corresponds to the formula:##STR3## or its tautomeric form, wherein X represents a carbon atom or aheteroatom such as sulphur, oxygen or nitrogen, A represents thecomplementary atoms required to form an unsaturated ring which maycontain one or more heteroatoms and M represents a hydrogen atom, analkali metal, an alkaline earth metal or an ammonium group.

For example, M may be chosen from amongst lithium, potassium, sodium,calcium or magnesium or the groups (CH₃)₄ N⁺, (C₂ H₅)₄ N⁺, etc.

According to the invention, compound (1) is a bleaching acceleratorcompound chosen from amongst the azole, diazole, triazole or tetrazolederivatives substituted with a thiol radical. These compounds areparticularly active through the presence of the --N═C--S⁻ grouping orits tautomeric form. The preferred bleaching accelerator compounds ofthe invention are, for example, 1,2,4 triazol-3-thiol,1,2,3-triazol-4-thiol, 1,2,3,4-tetrazol-5-thiol and glyoxaline-2-thiol.

Another object of the present invention is a photographic productcomprising, in addition to the image-forming emulsion layers, a nonlight-sensitive top layer consisting of an emulsion comprising silverhalide grains with a size of less than 0.5 μm and a bromide content ofbetween 30 and 70% molar.

The top layer of the photographic product according to the inventionconsists of a fine-grain emulsion; this emulsion is preferablymonodisperse.

In the present description, monodisperse emulsions means emulsions, thecoefficient of variation (COV) of whose grain sizes is less than 35%,the coefficient of variation being defined by the formula:

    COV=σ·100/D

in which σ is the standard deviation and D the mean size of the grains,represented by the mean diameter when the grains are spherical or by themean value of the diameters of circular images having the same surfacearea as the projected images of the grains, when they are not spherical.

The mean equivalent diameter of the grains which make up the emulsion ofthe top layer is preferably between 0.1 and 0.3 μm. The emulsion of thetop layer according to the invention is a bromochloride emulsion with abromide content preferably between 45 and 55% molar. The coverage of thetop layer is between 0.05 and 0.5 mg/dm².

The color photographic products which are used in the present inventiongenerally comprise a base bearing at least one blue-sensitive silverhalide emulsion layer with which a yellow dye forming coupler isassociated, at least one green-sensitive silver halide emulsion layerwith which a magenta dye forming coupler is associated, and at least onered-sensitive silver halide emulsion layer with which a cyan dye formingcoupler is associated, and the top layer of the invention.

These products can contain other conventional layers in the photographicproducts such as spacing layers, filtering layers, anti-halo layers andimmobilising layers. The base can be any suitable base used withphotographic products. Conventional bases comprise polymer films, paper(including polymer-coated paper), glass and metal. Research Disclosure,December 1978, No 17643, Section XVII, provides details about bases andadditional layers for photographic products.

The preparation of silver halide emulsions is described , for example,in Research Disclosure, No 17643, Sections I and II. Silver halideemulsions can be chemically sensitised in accordance with the methodsdescribed in Section III of the Research Disclosure referred to above.The chemical sensitisers generally used are compounds of sulphur and/orselenium and gold. It is also possible to use sensitisation byreduction. The halide grains can have different compositions. Forexample, it is possible to use grains of silver bromide, silveriodobromide, silver chloride, silver chloroiodide or silverchlorobromoiodide. The silver halide grains can be spherical, cubic,octahedral, cubo-octahedral or tabular. The silver halide grains can beof the core/shell type, for example as in U.S. Pat. No. 3,505,068, orcan include epitaxial deposits as in U.S. Pat. No. 4,713,320. Thesesilver halide emulsions can in addition contain doping agents, generallyin small quantities, such as rhodium, indium, osmium, etc ions.

The silver halide emulsions and other layers on the photographicproducts of this invention can contain, as a vehicle, hydrophiliccolloids, used alone or in combination with other polymeric substances(for example latexes). Suitable hydrophilic substances comprise naturalsubstances such as proteins, protein derivatives, cellulose derivatives,for example cellulose esters, gelatin, for example gelatin treated witha base (cattle gelatin, bone or tanned) or gelatin treated with an acid(pigskin gelatin), gelatin derivatives, for example acetylated gelatin,phthalated gelatin, etc, polysaccharides such as dextran, gum arabic,zein, casein, pectin, collagen derivatives, collodion, agar-agar andalbumin.

The emulsions can be polydisperse or monodisperse or can consist of amixture of emulsions with different grain sizes and/or dispersities.

The spectral sensitisation, or chromatisation, methods are described inthe same publication, Section IV. The sensitising dye can be added atvarious stages of preparation of the emulsion, in particular before,during or after the chemical sensitisation.

The silver halide emulsions can be sensitised spectrally with dyes fromvarious classes, including the class of polymethine dyes, whichcomprises cyanines, merocyanines, complex cyanines and merocyanines(that is to say tri-, tetra-, and polynuclear cyanines andmerocyanines), oxonols, hemioxonols, styryls, merostyryls andstreptocyanines. Research Disclosure, No 17643, mentioned above, SectionIV, describes the representative spectral sensitising dyes.

The photographic products of the invention can contain, amongst otherthings, optical brighteners, antifogging agents, surfactants,plasticisers, lubricating agents, tanning agents, stabilisers andabsorption and/or diffusion agents as described in Sections V, VI, VIII,XI, XII and XVI of the Research Disclosure referred to above.

The methods of adding these different compounds and the coating anddrying methods are described in Sections XIV and XV.

According to the invention, the color photographic products comprise, ina conventional manner, at least three constituents which arerespectively blue, green and red-sensitive and supply respectively theyellow, magenta and cyan components of the color image subtractivesynthesis.

According to one embodiment, the photographic products of the inventionare reversible products and the processing method of the invention is areversal method.

The reversible products of the invention preferably comprise at leastone layer comprising a polydisperse sensitive emulsion. Thispolydisperse emulsion is preferably highly sensitised and associatedwith one or more slower monodisperse emulsions with a COV of less than35%. The other layers of the photographic product comprise one or moremonodisperse emulsions with a COV of less than 35% and whose mean sizevaries according to the speed desired. These monodisperse emulsions canbe prepared by double-jet precipitation in the presence of a solvent ofsilver halides such as a thioether, thiourea or thiocyanate. It is alsopossible to use core/shell monodisperse emulsions, in which the core andshell have variable halide contents, for example emulsions whose core isformed by silver bromoiodide and whose shell contains a quantity ofiodide less than that of the core, which can be equal to zero. Suchemulsions have been described, for example, in U.S. Pat. Nos. 3,206,313and 3,505,068 and in French Patent 1 367 941.

In a preferred embodiment, the monodisperse emulsions are emulsions withan octahedral core/shell structure of silver bromoiodide containing intotal less than 10% molar of iodide, and preferably 3 to 5% molar ofiodide, doped with iridium. These monodisperse emulsions are chemicallysensitised in a conventional manner, as indicated in ResearchDisclosure, December 1989, No 308119, Section IIIA, and spectrally asindicated in the same reference, Section IV.

Each chromatised constituent of the product can comprise at least twoemulsions, and preferably three emulsions, with different speeds, thatis to say a fast emulsion and a slow emulsion, or else a fast one, amedium one and a slow one. These emulsions are mixed in a single layeror introduced in separate layers.

The reversible products, after being exposed, undergo photographicprocessing comprising a silver development of the latent image (blackand white development), then a reversal, which consists of making thenon-exposed residual silver halide grains developable by a foggingexposure or chemical fogging, and subjecting these fogged silver halidegrains to a color development, in the presence of a color developer anda coupler, the latter generally being incorporated in the reversibleproduct.

The photographic products are then washed and put through a bleachingbath and then a fixing bath, before being processed in a stabilisingbath.

The silver development takes place in the presence of a reducingcompound which makes it possible to transform the exposed silver halidegrains into metallic silver grains. These compounds are chosen fromamongst the dihydroxybenzenes such as hydroquinone, the 3-pyrazolidones,the aminophenols, etc. These compounds can be used alone or in amixture. This first bath can, moreover, contain a stabiliser such assulphites, and a buffer such as carbonates, boric acid, borates oralcanolamines.

The reversal stage is usually carried out chemically, either by passingthrough a fogging bath containing a reducer, or by introducing thefogging agent into the color bath. The fogging substances are, forexample, stannous chloride, hydrazine and semi-carbazide salts, ethylenediamine, sodium borohydride, dimethyl borane or thiourea dioxide.

The color developer contained in the color developing bath, which makesit possible to obtain the color image, is in general an aromatic primaryamine such as the p-phenylenediamines, especially theN,N-dialkyl-p-phenylenediamines or an alkyl radical, and the aromaticring can be substituted or not. The p-phenylenediamines used as colordevelopers are, for example, N,N-diethyl-p-phenylenediaminemonochlorhydrate, 4-N,N-dimethyl-2-methylphenylenediaminemonochlorhydrate, 4-(N-ethyl-N-2-hydroxyethyl)-2-methylphenylenediaminesulphate. This color developing bath can contain other compounds such asstabilisers or development accelerators which are generally pyridiniumcompounds or other compounds.

The essential compound in the bleaching bath is an oxidising compoundwhich converts the metallic silver into silver ions such as, forexample, the alkali metal salts of a ferric complex of anaminocarboxylic acid, or persulphate compounds.

The bleaching compounds normally used are the ferric complexes ofnitrolotriacetic acid, ethylenediamine tetracetic acid,1,3-propylenediamine tetracetic acid, triethylenetriamine pentaceticacid, ortho-diamino cyclohexane tetracetic acid, ethyliminodiaceticacid, etc.

The fixing bath makes it possible to convert the silver halidecompletely into a soluble silver complex which is then eliminated fromthe layers on the photographic product. The compounds used for fixingare, for example, thiosulphates, such as ammonium thiosulphates, oralkali metals. Stabilising agents and sequestering agents can be addedto the fixing bath.

The bleaching bath and fixing bath can be replaced with a singlebleach-fixing bath. The bleaching accelerating compound is generallyeither in the bleaching bath or in the bleach-fixing bath. Theprocessing generally comprises a stabilising bath containing a colorstabiliser such as formaldehyde, and a wetting agent.

In the following examples, the color reversible photographic productsare exposed and processed in accordance with the standard Ektachrome™R-3 process.

EXAMPLE 1

The photographic products used in the examples of the invention compriseemulsion layers according to the following structure, applied to a paperbase covered with polyethylene:

    ______________________________________                                        Anti-UV layer                                                                 Blue-sensitive emulsion layer                                                 comprising a yellow coupler                                                   Fast                 Polydisperse emulsion                                    Slow                 Core/shell monodisperse                                                       emulsion (0.7 μm)                                     Filter layer comprising yellow colloidal silver                               Green-sensitive emulsion layer                                                comprising a magenta coupler                                                  Fast                 Polydisperse emulsion                                    Medium               Core/shell monodisperse                                                       emulsion (0.7 μm)                                     Slow                 Core/shell monodisperse                                                       emulsion (0.43 μm)                                    Layer containing grey colloidal silver                                        Red-sensitive emulsion layer comprising                                       a cyan coupler                                                                Fast                 Core/shell monodisperse                                                       emulsion (1.07 μm)                                    Medium               Core/shell monodisperse                                                       emulsion (0.43 μm)                                    Slow                 Core/shell monodisperse                                                       emulsion (0.38 μm)                                    Gelatin + Non-sensitive fine-grain emulsion                                   BASE                                                                          ______________________________________                                    

The polydisperse emulsion is an emulsion containing octahedral silverbromoiodide grains with an iodide content of less than 5% and a meanequivalent diameter of the order of 1 μm, preferably highly sensitised.This emulsion can be prepared and sensitised in accordance with themethod described in European patent application 91912604.5.

The monodisperse core/shell emulsions (COV≦35%) comprise octahedralgrains containing a total iodide content of less than 5%, the iodidebeing located mainly in the core.

The emulsion of the layer in contact with the base is an emulsioncontaining non light-sensitive silver halide grains (of the order of0.11 μm) prepared in accordance with the method described in Chimie etPhysique Photographique, by P Glafkides, 4th Edition, page 481.

EXAMPLE 2 Preparation of the emulsions in the top layer

The fine-grain emulsion in the top layer of the invention is prepared inaccordance with the following procedure:

In a 20 liter reactor, 3.7 liters of distilled water, 98.5 g of gelatinand 175 mg per mole of silver of a thioether solvent are introduced, andthis solution is adjusted to a pAg equal to 8 by the addition of asolution of NaCl and to a pH of 5.5 at 38° C.

Nucleation is effected by double-jet precipitation from a solution ofAgNO₃ (3.05 mol/l) and a solution of NaCl/NaBr in a ratio of 50:50(3.293 mol/l) for a period of 35 seconds at a constant pAg.

Precipitation is then carried out by the double-jet method at a constantrate for 15 minutes with the same solutions, the temperature beingmaintained at 38° C. and the pAg at 8.5 moles of an AgBrCl (50:50)monodisperse emulsion is obtained. The emulsion is then washed byconventional flocculation methods. This fine-grain emulsion consists ofcubo-octahedral grains with a mean equivalent spherical diameter of 0.11μm.

100% chloride and 100% bromide emulsions were prepared by the samemethod, as well as a chlorobromide emulsion containing 30% bromide.

EXAMPLE 3

Each of the emulsions prepared in Example 2 is applied to thephotographic product whose structure was described above in Example 1with a coverage of 0.15 mg/dm².

The products obtained in this way are exposed to light from a tungstenlamp (2850° K.). They are then processed in an AUTOPAN™ automaticprocessing machine comprising conventional Ektachrome™ R-3 processingbaths, except that increasing quantities of 1,2,4-triazol-3-thiol wereadded to the first developer.

A reference photographic product having the structure described above inExample 1 and not comprising any top layer is processed in the same way.

The standard Ektachrome™ R-3 processing comprises the following stages:

    ______________________________________                                        Black and white development                                                                             1 min 15                                            Washing                   1 min 30                                            Re-exposure Color development (38° C.)                                                           2 min 15                                            Washing                   0 min 45                                            Bleach-fixing             2 min                                               Washing                   2 min 15                                            ______________________________________                                    

For each photographic product, the following sensitometriccharacteristics are measured:

1) the sensitivity obtained for a density of 0.8 calculated by means ofthe formula ER₀.8 =100 (1-LogE₀.8),

2) the shoulder density which is represented by the density at anexposure of less than 0.5 LogE at the exposure giving a density of 0.8,hereinafter referred to as 0.5 SD,

3) the toe density which is represented by the density at an exposuregreater than 0.4 LogE at the exposure giving a density of 0.8,hereinafter referred to as 0.4 TD, and

4) the toe density which is represented by the density at an exposuregreater than 0.8 LogE at the exposure giving a density of 0.8,hereinafter referred to as 0.8 TD.

All these measurements are made for each sensitometric curvecharacterising each layer, sensitive respectively to red, green and blueradiation.

For each layer, a graph is traced which represents the variations ineach sensitometric characteristic defined above versus the quantity of1,2,4-triazol-3-thiol in the first developer expressed in mg/l, takingas a reference the values of the sensitometric characteristics obtainedwhen the first developer does not contain any 1,2,4-triazol-3-thiol.

FIGS. 1A, 1B, 1C and 1D (reference) show the variations in thesensitometric characteristics defined above for each sensitive layer ofthe photographic product described previously which does not contain anytop layer, versus the quantity of 1,2,4-triazol-3-thiol, which variesbetween 0 and 5 mg/l.

FIGS. 2A, 2B, 2C and 2D (comparison) show the variations in thesensitometric characteristics defined above of each sensitive layer ofthe photographic product described previously comprising a top layer of100% chloride emulsion, versus the quantity of 1,2,4-triazol-3-thiol,which varies between 0 and 5 mg/l.

FIGS. 3A, 3B, 3C and 3D (invention) show the variations in thesensitometric characteristics defined above of each sensitive layer ofthe photographic product described previously comprising a top layer of30% bromide emulsion versus the quantity of 1,2,4-triazol-3-thiol, whichvaries between 0 and 5 mg/l.

FIGS. 4A, 4B, 4C and 4D (invention) show the variations in thesensitometric characteristics defined above of each sensitive layer ofthe photographic product described previously comprising a top layer of50% bromide emulsion, versus the quantity of 1,2,4-triazol-3-thiol,which varies between 0 and 5 mg/l.

5A, 5B, 5C and 5D (comparison) show the variations in the sensitometriccharacteristics defined above of each sensitive layer of a photographicproduct described previously comprising a top layer of 100% bromideemulsion versus the quantity of 1,2,4-triazol-3-thiol, which variesbetween 0 and 5 mg/l.

Comparing the variations in the sensitometric characteristics observed,it can be noted that the addition of a top layer of the invention to acolor photographic product makes it possible to control the sensitivityduring processing in the presence of the contaminating compound.

In fact, it has been possible to show that the variations in thesensitometric characteristics of the photographic products of theinvention remain small even when they are processed in a first developerhaving a concentration of contaminating compound as high as 5 mg/l.

Moreover, this top layer makes it possible to avoid any rapiddeterioration in the effectiveness of the first developing bath.

We claim:
 1. A method for controlling the sensitivity of a colorphotographic product during photographic processing, said colorphotographic product comprising a base, at least one light-sensitivesilver halide emulsion layer and a top layer of non light-sensitivesilver halide emulsion, wherein the exposed product is processed in ableaching or in a bleach-fixing bath, characterised in that (A) the toplayer of the photographic product consists of an emulsion comprisingsilver chlorobromide grains having a size of less than 0.5 μm and abromide content of between 45 and 55% molar, and (B) said bleaching orbleach-fixing bath initially comprising a bleaching accelerator compound(1) defined by the formula: ##STR4## in which X represents a nitrogen, Arepresents the complementary atoms required to form an unsaturated ringwhich may contain one or more heteroatoms and M represents a hydrogenatom, an alkali metal or an ammonium group, provided that saidunsaturated ring is an azole, diazole, triazole or tetrazole ring.
 2. Amethod according to claim 1 wherein the bleaching accelerator compoundis 1,2,4-triazole-3-thiol.
 3. A method according to claim 1, wherein thesilver halide grains in the top layer have a mean size of between 0.1and 0.3 μm.
 4. A method according to claim 1 wherein the bromide contentis about 50% molar.
 5. A method according to claim 3, wherein thecoverage of the top layer is between 0.05 and 0.5 mg/dm².
 6. A methodaccording to claim 1, wherein the color photographic product comprisesat least one photographic emulsion consisting of silver halide grainshaving a core/shell structure.
 7. A method according to claim 1, whereinthe color photographic product comprises at least one silver bromoiodidephotographic emulsion.
 8. A method according to claim 1, wherein thecolor photographic product comprises at least one monodispersephotographic emulsion.
 9. A method according to claim 1, wherein atleast one of the light-sensitive layers consists of a mixture ofphotographic emulsions with different sensitivities.
 10. A methodaccording to claims 1, for the processing of reversible colorphotographic products.
 11. The method of claim 1 wherein said bleachingaccelerator compound (1) is present in said bleaching or bleach-fixingfixing bath in an amount of up to 5 mg/l.
 12. The method of claim 1wherein said bleaching accelerator compound (1) is1,2,4-triazole-3-thiol, 1,2,3-triazole-4-thiol,1,2,3,4-tetrazole-5-thiol or glyoxaline-2-thiol.
 13. A method forcontrolling the sensitivity of a color photographic product duringphotographic processing, said color photographic product comprising abase, at least one light-sensitive silver halide emulsion layer and atop layer of non light-sensitive silver halide emulsion, wherein theexposed product is processed in a bleaching or in a bleach-fixing bath,characterised in that (A) the top layer of the photographic productconsists of an emulsion comprising silver chlorobromide grains having asize of less than 0.5 μm and a bromide content of between 45 and 55%molar, and (B) said bleaching or bleach-fixing bath initially comprising1,2,4-triazole-3-thiol as a bleaching accelerator compound.
 14. A methodfor controlling the sensitivity of a color photographic product duringphotographic processing, said color photographic product comprising abase, at least one light-sensitive silver halide emulsion layer and atop layer of non light-sensitive silver halide emulsion, wherein theexposed product is processed in a bleaching or in a bleach-fixing bath,characterised in that (A) the top layer of the photographic productconsists of an emulsion comprising silver chlorobromide grains having asize of less than 0.5 μm and a bromide content of between 45 and 55%molar, and (B) said bleaching or bleach-fixing bath initially comprising1,2,4-triazole-3-thiol, 1,2,3-triazole-4-thiol,1,2,3,4-tetrazole-5-thiol or glyoxaline-2-thiol as a bleachingaccelerator compound.